4+2/4 in Gonville

I think this is a bug:

I can define the 4+2/4 time signature by using 6/4 and specifying 4+2/4 in the text boxes. The correct symbol appears in the cleft pallet but when I drop the cleff onto a stave it renders as 42/4 omitting the + sign.

I'm using Gonville. In other fonts this process works.

Richard